Week 14 Cold Revisit

This Friday, before any new work, re-solve two prior problems cold: no notes, no prior code open, no AI, the standard 25-minute struggle floor on each. The first solve taught the pattern; this blind re-solve is what makes it stick.

The two problems

  1. Merge Intervals (Week 10, Tries and Intervals). https://leetcode.com/problems/merge-intervals/
  2. Coin Change (Week 13, 1-D Dynamic Programming). https://leetcode.com/problems/coin-change/

How to run the revisit

  • Do not look up which pattern either problem belongs to. Recognizing it cold, from the problem statement alone, is the entire point of the exercise; the tutor will not tell you.
  • Start each from a blank file. Name the pattern aloud, write the plain-English approach as a comment, then code.
  • Apply the 25-minute floor to each independently. If you stall past the floor, use the hint ladder, one rung per ask.
  • Submit each to LeetCode’s judge. The judge is the oracle, not the tutor.
  • Debrief each with the five questions in your commit message, and log the outcome in .tutor/revisit-log.md.

These two are chosen on purpose, and they pull in different directions. Merge Intervals is the Intervals pattern from four weeks back, which no Friday has pulled back since you met it: the test is cross-course recognition, reaching past this week’s pattern to the sort-by-start-then-sweep move (sort the intervals, then walk left to right and fold each one into the previous if they overlap). Coin Change is last week’s canonical DP problem at a deliberately short interval: the test is retention, whether the five-step framework still fires now that 1-D DP is no longer the pattern you are living in. One of them is DP and one is not, and you should not know which until you have read each statement cold and named it yourself. If either comes back slower than you expect, that is the signal for where to spend your next stretch session.